Substitution of 3d metals for Cu in Bi2(Sr0.6Ca0.4)3Cu2Oy

Abstract

The effect of the substitution of 3d metals (Fe, Co, Ni, and Zn) for Cu in a high-temperature superconductor ${\mathrm{Bi}}_2$(Sr,Ca${)}_3$ ${\mathrm{Cu}}_2$ ${\mathrm{O}}_{\mathit{y}}$ was investigated by measuring lattice constants, dc resistivity, Hall effect, and magnetic susceptibilities in normal and superconducting phases. For all kinds of impurities, within the composition range where the single-phase samples are synthesized, the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ was found to decrease with increasing impurity concentration. Even nonmagnetic Zn was found to decrease ${\mathit{T}}_{\mathit{c}}$, as well as, magnetic Fe, Co, and Ni, without changing the hole concentration. These behaviors cannot be explained by the Abrikosov-Gorkov theory for conventional BCS superconductors. Possible explanations are discussed.